Cycles viewport render blank
I had the same problem and here is what I discovered: Under 'Properties > Output properties > Dimensions' I accidentally had the option 'Render region' checked. Once I unchecked this option, Cycles was back in bussiness. A simple solution but it can be very confusing if you don't know what's going on, since Eevee would render with this option checked. Hope some day this helps someone out there.